How To Support MacOS Internet
Understanding Internet Addressing
When using the Internet, you are assigned a Public IPv4 address, such as 90.158.93.87, or an IPv6 address, like 2000:6ed9:feea:42d1:d29:3eec:ccd4:8546. You can verify this by visiting https://test-ipv6.com/. However, explaining and conveying these addresses, as well as MAC addresses like 13:fd:fd:3c:e2:09, to those who are not tech-savvy can be prone to errors and quickly become complex. Moreover, it does not offer any historical data, especially when previous issues occurred.
Procedure for Accessing the Internet
In order to access a website, such as https://stanton.io, the first step is to contact a DNS server to convert the host portion (stanton) combined with the Top Level Domain (io) of the URL into an IP address, such as 150.220.199.175. When making web requests, your computer and browser send their type with every interaction, for example Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285
Significance of Default Gateways
By default, your gateway is an address that is automatically configured via DHCP. You are provided with a default gateway, such as 10.177.84.195 (though they usually ending in .1 or .254 based on the scope size), and this is where your computer sends all its traffic to be routed onwards. For IPv6, an in-depth guide is available on how-to-fix-ipv6-connectivity/, where you can also check on Mac or Linux with:
IPv4 Routes and the Host IPv4 Route Table (inc. VPN)
netstat -rn -f inet | egrep -i "default|0/1|128.0/1"
0/1 172.18.12.193 UGScg utun3 default 10.177.84.195 UGScg en0 128.0/1 172.18.12.193 UGSc utun3
Note: We are not just looking for the default but also for any VPN that overrides the public v4 address space.
IPv6 Routes and the Host IPv6 Route Table (inc. VPN)
netstat -rn -f inet6 | egrep -i "default|2000::/3"
If you have IPv6 active the above should return at least one route (as per below) via a known interface such as “en0 " on a Mac.
default fe80:3d5c:8802:ba77:e0fd%en0 UGcg en0 default fe80::%utun0 UGcIg utun0 default fe80::%utun1 UGcIg utun1 default fe80::%utun2 UGcIg utun2 2000::/3 utun3 USc utun3
Note: We are not just looking for the default but also for any VPN that overrides the public v6 address space.
Debugging DHCP for both IPv4 and IPv6
To get a look at the low level DHCP configuration (Mac/Linux):
ipconfig getpacket en0
...
domain_name_server (ip_mult): {254.13.8.186, 204.200.94.9}
end (none):
...
So, in the above we are not getting IPv6 DNS servers from the DHCPv4 reply but…
ipconfig getv6packet en0
DHCPv6 REPLY (7) Transaction ID 0x80940b Length 76
Options[4] = {
CLIENTID (1) Length 14: DUID LLT HW 1 Time 668691856 Addr 13:fd:fd:3c:e2:09
DNS_SERVERS (23) Length 32: 2606:4700:4700::1111, 2001:4860:4860::8844
DOMAIN_LIST (24) Length 0: Invalid
SERVERID (2) Length 10: DUID LL HW 1 Addr 5b:71:6d:1c:25:d4
}
Resolve Connection Issues with Wired and Wireless Networks
When transmitting data to your router, you may be utilizing a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Methods for Apple macOS / OSX
Regardless of which version of OSX/macOS you are using, whether it’s 10.13.8, 11.2.5, or 12.0.2, there are various tools available for resolving issues. However, these tools don’t provide a series of correlated values over time, which is essential for effective troubleshooting. This is where automated remote troubleshooting becomes invaluable, especially for teams that embrace remote work and Work From Anywhere (WFA).
Utilize the In-Built Scripts
A useful tool on OSX/macOS is sudo wdutil info, which offers a dump of the current wireless settings to the CLI, and can also be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only relevant to wireless settings at a specific point in time, similar to wdutil.
To run sysdiagnose in the background and write logs to /var/tmp/<blah>.tar.gz, execute the command: sudo nohup /usr/bin/sysdiagnose -u &. For an interactive experience (despite minimal interaction), you can run: sudo /usr/bin/sysdiagnose and it will give a privacy warning. When not run in the background, it should open Finder in the correct location, or you can manually navigate to /var/tmp using Finder with Cmd+Shift+G. Be mindful of the file sizes, which are typically around 300MB.
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